The present invention relates to an air exhausting cap structure in a case such as an electric connection box.
For example, in an electric connection box of an electric car, when a temperature in the box is changed by heat generation of a mounted fuse, relay or the like, the air pressure in the box is changed so that an intake/exhaustion phenomenon occurs through a gap or the like by a pressure difference with respect to the outer air. Thus, in such a container (case), it is positively necessary to provide a communication path for balancing the inner pressure with the outer air. On the other hand, in a car, the waterproof property of a portion communicating with the outer air is an important problem. As an example of a structure in which such ventilation property and water proof property are compatible with each other, one disclosed in Japanese Utility Model Unexamined Publication No. Sho. 63-35268 will be described with reference to FIG. 6.
FIG. 6 is a sectional view showing a conventional air exhausting structure.
A ventilation tube 3 of a distributor cap is covered with a ventilator 5. The ventilator 5 includes a through path 7 opened to the outside in the vertical direction. In the ventilator 5, a containing chamber 9, which is a laterial expansion of the through path 7, is formed. In the containing chamber 9, a ventilation hole 11 of the ventilation tube 3 is opened. The through path 7 orthogonally intersects the ventilation hole 11 at an upper horizontal space 13. The entire of a ventilation path is bent. According to this structure, the through path 7 communicates with the ventilation hole 11 so that the inside of the distributor communicates with the outer air.
In this structure, when water 15 falls to the ventilator 5 so that it enters into the through path 7, the water 15 drops to the lower side as it is as shown by an arrow of a solid line and is drained from a lower end of the through path 7 to the outside. At this time, the outer air is bent at the upper horizontal space 13, and communicates with the inside of the distributor through the ventilation hole 11 as shown by an arrow of a dotted line. That is, the outer air is separted from the water in the portion of the upper horizontal space 13, so that the intrusion of the water 15 into the ventilation hole 11 is prevented. The exhaustion gas in the heated distributor passes through the upper horizontal space 13 in the direction opposite to the arrow of the dotted line and is exhaused to the outside through the through path 7.
However, in the above described conventional air exhausting structure, the upper horizontal space 13 orthogonally intersects the through path 7 opened to the outside, the water 15 dropped into the through path 7 is separated from the outer air by gravity, and only the outer air is led to the upper horizontal space 13. Thus, when minute water drops 15a are attached to an inner wall of the through path 7, there occurs a case in which the attaching force becomes larger than the gravity and the water drops are guided along the inner wall of the upper horizontal space 13 and flown into the ventilation hole 11. Also, there is a problem that when the pressure in the distributor becomes negative, an air stream flowing from the through path 7 into the upper horizontal space 13 is generated and the water 15 intrudes into the upper horizontal space 13 according to this air stream so that separation by the gravity is not sufficiently performed.